While Bacteroides gingivalis appears to play a central role in the complex microbial interactions associated with periodontitis, there are essentially no data which indicate how this microorganism establishes itself in a susceptible host to eventually participate in the disease process. Bacterial adherence is a prerequisite for both the establishment of many host- associated microorganisms and their subsequent virulence. Although B. gingivalis adheres to certain other microorganisms, the potential role of this type of interaction in the establishment and emergence of this organism remains largely unexplored. This research will examine the interbacterial adherence of B. gingivalis with selected members of the subgingival microbiota, and will attempt to identify and characterize cell surface molecules (i.e., adhesins) of potential importance in the emergence of this microorganism. The Physician-Scientist Award will provide the Principal Investigator with the didactic education (Phase I) and laboratory training (Phase I and II) required for studies on the complex biological interactions. Importantly, in both phases of this training program, it will expose the Principal Investigator to individuals and departments whose research interests are in molecular pathogenesis. The research proposed will examine the adherence of B. gingivalis to selected periodontal microorganisms which are known to be established in the peroidontal pocket prior to the emergence of B. gingivalis with a co-aggregation technique (Specific Aim 1). Surface structures potentially involved in B. gingivalis adherence will be isolated and characterized biochemically and immunologically (Specific Aim 2). A comprehensive examination of the specific adherence of B. gingivalis to one or more test strains will be carried out to delineate those surface molecules functioning as adhesins (Specific Aim 3). The B. gingivalis adhesin(s) will be further characterized by recombinant DNA technology to delineate or isolate the gene(s) responsible for their production (Specific Aim 4). It is the long range goal of this research (but beyond the scope of this award) to examine the role of interbacterial adherence in in vivo models of periodontitis, leading potentially to the development of strategies to interfere with the establishment of this microorganism in the subgingival environment, and possibly to interfere with disease development.